A robust sliding mode controller design for a ball screw table driven by an air motor

Air motors are often applied in the automation industry in areas with special requirements, such as in spark-prohibited environments, the mining industry, chemical manufacturing plants, and similar locations. The purpose of this study is to analyze the behaviors of a ball screw table powered by a vane-type air motor and to design a robust sliding mode controller for the inlet pressure. The rotational speed of the air motor is closely related to the pressure and flow rate of the compressed air. Furthermore, the compressibility of the air and the friction in the mechanism mean that the overall system is nonlinear, with fluctuating input. A robust sliding mode control is developed to overcome the effects of variations in the inlet pressure and air leakage problems. The experimental results validate the robustness of the proposed position control strategy.